Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
Volume 61, Issue 7
July
Displaying 1-8 of 8 articles from this issue
Special Issue: Research Progress and New Development of Hard Materials Concerning Microstructure, Properties and Process
Summarization
Memorial Lecture of JSPM Award
  • Hitoshi SUMIYA
    2014 Volume 61 Issue 7 Pages 349-354
    Published: July 15, 2014
    Released on J-STAGE: August 25, 2014
    JOURNAL OPEN ACCESS
    ABSTRACT

    Novel ultra-hard materials: single-phase (binderless) polycrystalline diamond and cBN, have been produced by direct conversion sintering under static high pressure and high temperature. The polycrystalline diamond and cBN consist of fine grains of several tens or hundreds nano-meters without containing any secondary phases or binder materials. They have high hardness and high strength which surpass those of their single crystals and conventional sintered compacts containing binder materials. The fine microstructure features without any secondary phases and surpassing mechanical properties of the single-phase polycrystalline diamond and cBN are promising for applications in next-generation high-precision and high-efficiency cutting tools.
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Paper
  • Hiroyuki HOSOKAWA , Kiyotaka KATO, Koji SHIMOJIMA, Ryoichi FURUSHIMA, ...
    2014 Volume 61 Issue 7 Pages 355-361
    Published: July 15, 2014
    Released on J-STAGE: August 25, 2014
    JOURNAL OPEN ACCESS
    ABSTRACT

    The microstructures of Ti(C0.7N0.3)–19Mo2C-xNbC–24Ni cermets (x = 0, 5, 10, 15, 20) were studied. The microstructures of them consisted of hard phase with Ti(C, N) and solid soluted Ti(C, N), and Ni binder phase. The solid soluted Ti(C,N) surrounded Ti(C, N), namely, core-rim structures in the cermets with low NbC contents. The phase separation between Ti(CN) core and solid soluted Ti(C, N) occurs in the cermets with high NbC contents. As a result of TEM analysis, solid soluted Ti(C, N) nucleated surrouunding Ti(C, N) in the 5NbC, on the other hand, another site in the 20NbC. The content of Nb in solid soluted Ti(C, N) in the 20NbC was higher than that in 5NbC. The hard phase separation occurred when the lattice constant of solid soluted Ti(C, N) was beyond 4.328 Å.
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  • Kumiko TANAKA, Katsuhiro NISHIYAMA
    2014 Volume 61 Issue 7 Pages 362-368
    Published: July 15, 2014
    Released on J-STAGE: August 25, 2014
    JOURNAL OPEN ACCESS
    ABSTRACT

    An experimental study for obtaining a high performance ceramics of titanium diboride and tungsten carbide composites (TBWC) are described. WC content 10 to 90 volume percent tungsten was examined. The TBWC is inexpensive and can be fabricated by a hotpress-sintering process. The TBWC with density 95 % and above of the theoretical value were obtained using constituent powder of micron size by hotpress sintering. The TBWC thus obtained consists of four phases which are (Ti, W)B2, (W, Ti)C and 2 types of (W, Ti)B. Unlike porycrystalline diamond and cBN compacts, in which the intrinsic hardness or strength of the constituents is utilized, it seems that the TBWC is basically hardened or strengthend by solution hardening or dispersion strengthening mechanisms. Those mechanisms were confirmed by metallography, X-ray diffraction, electron probe microanalysis and mechanical tests.
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  • Yotaro HIRABAYASHI, Shinji TAKEUCHI, Atsushi HIBINO
    2014 Volume 61 Issue 7 Pages 369-377
    Published: July 15, 2014
    Released on J-STAGE: August 25, 2014
    JOURNAL OPEN ACCESS
    ABSTRACT

    TiAl base and Ni3Al base composite intermetallic compounds were investigated by Two-step combustion synthesis process. In TiAl–Ni3Al composite compound by the combustion synthesis, the products contain Ti2NiAl3 (τ3)and TiNi2Al (τ4) phases, and spoil the mechanical properties of the composite compound material. Therefore, Two-step combustion synthesis of TiAl base and Ni3Al base composite compounds were examined in compositions near the TiAl and Ni3Al of the Ti–Ni–Al system
    Elemental (Ti+Al) premixed compact was made to react by thermal explosion reaction as first step combustion synthesis. The synthesized TiAl product was grinded, and mixed with elemental Ti, Ni and Al powders again. The (TiAl+Ti+Ni+Al) mixed compact was made to react by thermal explosion reaction as second step combustion synthesis. For the products obtained, density, phase, microstructure, Vickers hardness, and compression strength were measured.
    By using Two-step combustion synthesis, TiAl base and Ni3Al base composite compounds could be fabricated. The TiAl base composite intermetallic compounds were so hard and so weak, to use for mechanical material. However Ni3Al base composite compounds contained a few Ti component exhibited superior ductility. Therefore, it was found that the addition of Ti component into Ni3Al is effective for improving the mechanical properties of Ni3Al compound.
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